1. Field of the Invention
A spark-ignition engine has self-adaptive adjustment of the size of its fuel rations, in dependence on misfires in the engine.
2. Description of the Prior Art
It has been found that the specific fuel consumption of a spark-ignition engine can be reduced by burning a lean fuel-air mixture. If the mixture is too lean, however, the engine will misfire on some of its combustion cycles. Excessive misfiring will increase the specific fuel consumption and the atmospheric emission of unburned hydrocarbons. Thus it is important for both fuel economy and low atmospheric pollution that the fuel-to-air ratio be maintained within a rather narrow range.
One method for rationing fuel and air in the correct ratio is to use a carburetor. In the carburetor a fuel reservoir at atmospheric pressure supplies fuel to the air stream through a metering orifice, the pressure drop across the metering orifice being produced by the rush of the air stream through a Venturi tube.
Other methods for rationing fuel employ continuous or timed fuel injection, in which the pressure in a fuel reservoir is kept well above atmospheric pressure. A separate fuel metering orifice is commonly used for each cylinder, the fuel entering the air stream immediately in front of the air intake valve for that cylinder. In the case of timed fuel injection, an on-off valve is associated with each metering orifice, the size of the fuel ration being varied by changing the length of time that its valve is open during each combustion cycle.
These methods of rationing fuel require metering orifices whose flow characteristics are constant in time. However, during the life of the engine the metering orifices may become fouled so that their flow characteristics change, seriously affecting the engine's specific fuel consumption and atmospheric emission. It is then necessary to test and adjust or to replace the metering orifices.
Self-adaptive apparatus for regulating the fuel-to-air ratios of a multicylinder engine are disclosed in my copending patent application Ser. No. 200,369, filed Oct. 24, 1980. These apparatus automatically vary the fuel-to-air ratio in each individual cylinder in dependence on misfires in that cylinder. Misfires in a particular cylinder are detected by comparing the energy of its explosion with the energy of explosions in other cylinders.